now that loads are in their own table, we can implement
store->load forwarding. This allows EarlyCSE to zap 600 more
loads from 176.gcc.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122732 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/EarlyCSE.cpp b/lib/Transforms/Scalar/EarlyCSE.cpp
index a899640..06c1b91 100644
--- a/lib/Transforms/Scalar/EarlyCSE.cpp
+++ b/lib/Transforms/Scalar/EarlyCSE.cpp
@@ -380,8 +380,19 @@
// Okay, this isn't something we can CSE at all. Check to see if it is
// something that could modify memory. If so, our available memory values
// cannot be used so bump the generation count.
- if (Inst->mayWriteToMemory())
+ if (Inst->mayWriteToMemory()) {
++CurrentGeneration;
+
+ // Okay, we just invalidated anything we knew about loaded values. Try to
+ // salvage *something* by remembering that the stored value is a live
+ // version of the pointer. It is safe to forward from volatile stores to
+ // non-volatile loads, so we don't have to check for volatility of the
+ // store.
+ if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ AvailableLoads->insert(SI->getPointerOperand(),
+ std::pair<Value*, unsigned>(SI->getValueOperand(), CurrentGeneration));
+ }
+ }
}
unsigned LiveOutGeneration = CurrentGeneration;